The likely passage of Democrats' climate plan will instantly bring a fresh political challenge: selling it to voters.

Why it matters: The midterm elections will be the first ever to unfold after enactment of sweeping climate legislation.

• "This is a totally unprecedented moment that we're finding ourselves in," said David Kieve, president of EDF Action, the political arm of the Environmental Defense Fund.

Catch up fast: The House is expected to approve the Senate-passed climate, health and tax package today, sending it to President Biden's desk.

• It contains roughly $370 billion for renewables, clean tech manufacturing, home efficiency, electric vehicles purchases, hydrogen development and much more.

What we're watching: How Democrats will campaign on the bill, how the GOP will attack it, and whether it's as much of a political asset as Democrats hope it will be.

• For Democrats, it will offer the chance to campaign on a promise kept, not just the potential that they might be able to pass climate legislation someday.

The legislation will play a prominent role in various environmental groups' midterm campaigns in tight races in states like Georgia, Nevada, New Hampshire and Pennsylvania.

• That includes the $100 million multi-group campaign around federal and state races conducted jointly by EDF Action Votes, the League of Conservation Voters (LCV) Victory Fund, Climate Power Action and others. It was announced in early June.
• "This will be an important message point to demonstrate that this is what can happen when pro-climate champs are in office," said Pete Maysmith, LCV's senior VP for campaigns.

The other side: Republican strategist Scott Jennings does not see Democrats getting a political lift from the legislation.

He said polls show the economy is the top issue for voters and cited studies that suggest the bill is not projected to have much effect on inflation.

• "I think if you're going to call something inflation reduction, and the bill itself doesn't have any meaningful impact on inflation between now and election day, which I don't think it will, you're going to probably end up owning that more than you'll own any success about global warming," he said.

Yes, but: Democratic officials and environmentalists are heavily emphasizing the economic dimensions themselves, especially the potential to lower consumers' energy costs.

• Creating jobs in clean energy-related construction and manufacturing will also be a focus.
• "The American people have understood that the jobs of the future are in clean energy, and they've said by a wide margin that they want those jobs to be here in the United States," said Kieve, of EDF Action.

The intrigue: Polling generally shows that climate change is not top of mind for most voters, coming in far behind the economy in questions about priorities.

But Kieve and others activists also note that climate is a highly motivating topic for some pockets of people.

• "Data point after data point tells us how much young voters care about climate change and want to see action on it," Maysmith, of LCV, said in an interview.
• Strategy will also vary by state and by district. For instance, environmentalists and Democratic operatives tell Axios provisions on addressing drought could help in competitive races in Arizona and Nevada.

Between the lines: One challenge for the bill's advocates is timing — the election will unfold very shortly after the bill has been signed into law, while the huge clean energy infrastructure expansion it envisions will take time.

• Says National Republican Senatorial Committee spokesman Chris Hartline: "I don't think any real voters are actually going to believe that anything in this bill is going to lower energy costs in the short term."